Phosphorylated inositols

ABSTRACT

A process for regioselectively preparing phosphorylated cyclitols, in particular phosphorylated inositols such as myo-inositol 1,4,5-tris(phosphate) and myo-inositol 1,3,4,5-tetrakis(phosphate). Novel cyclitols produced by means of this process are also described.

This is a divisional application of application Ser. No. 056,181 thatwas filed on May 29, 1987, now U.S. Pat. No. 4,873,355. BACKGROUND OFTHE INVENTION

1. Field of the Invention

The present invention discloses a process for regioselectively preparingphosphorylated cyclitols, in particular phosphorylated inositols such asmyo-inositol 1,4,5-tris(phosphate) and myo-inositol 1,3,4,5-tetrakis(phosphate). Novel cyclitols produced by means of this process are alsodescribed.

2. Background of the Invention

Cyclitols are cycloalkanes containing one hydroxyl group on each ofthree or more ring carbons. The most abundant members of the cyclitolfamily are the inositols (1,2,3,4,5,6-hexahydroxycyclohexanes) and themost important stereoisomer of this family is myo-inositol which has the1-, 2-, 3-, and 5-hydroxyl groups on one side of the ring and the 4- and6-hydroxyl groups on the other. Phosphorylated derivatives of cyclitolsand inositols, that is, those which have one or more hydroxyl groupsconverted to phosphate monoesters, are generally referred to,respectively, as cyclitol phosphates or inositol phosphates.

Cellular processes of all animals, including man, depend, at least inpart, upon inositol phosphates. Certain inositol phosphates function as"second messengers", that is, molecules which provide the means by whichneurotransmitters, growth factors or hormones alter processes insidecells without necessarily penetrating the cells they affect. When thecirculating hormone vasopressin binds to receptors on liver cells, forexample, it stimulates an increase in intracellular concentrations ofD-myo-inositol 1,4,5-tris(phosphate) and D-myo-inositol1,3,4,5-tetrakis(phosphate). The increased concentrations of thesesecond messengers in turn activates certain enzymatic processes withinthe cells. Similarly, Some growth factors such as platelet derivedgrowth factor (PDGF) cause increased production of inositol phosphatesin the cells they affect. Intracellular concentrations of inositolphosphates also appear to play a role in the regulation of cell divisionand the inflammatory response. Because of the potential medicinalimportance of the natural inositol phosphates, and analogs and isomersthereof, considerable research interest in these compounds has beengenerated. The National Library of Medicine's MEDLINE™ lists more than1400 published papers since 1980 on the subject of inositol phosphates.Recent reviews can be found in Science, 234: 1519 (1986) and ScientificAmerican, 253: 142 (1985).

Studies of inositol phosphates have been hindered by the limited amountsof material which are tediously isolated from natural sources. Practicalsynthetic routes for preparing significant amounts of these compounds ortheir analogs or isomers are not currently available. Research effortswould benefit greatly from the availability of adequate quantities ofisomerically-pure synthetic materials. An object of the presentinvention is to provide a synthetic process for the efficientpreparation of naturally occuring inositol phosphates and analogs andisomers thereof.

The broad steps utilized in art processes to synthesize phosphorylatedcylitols such as inositols are as follows. First, an inositol compoundhaving appropriately protected hydroxyl groups is obtained (Step 1).Next, the free hydroxyl groups in these precursors are converted tophosphate groups (Step 2), and finally, the hydroxyl protecting groupsare removed (Step 3). In practice, the second step frequently consistsof the following two stages: Step 2a, formation of a phosphorus-oxygenbond between the phosphorus of a "phosphorylating agent" (a compoundwhere the phosphorus is in the +5 oxidation state (P(+5)), and one ormore inositol oxygen; and Step 2b, removal of any protecting groupswhich are on the phosphorylating agent, hereafter referred to asphosphorus protecting groups. The crucial element in the synthesis ofthese compounds is the phosphorylation step (Step 2a) and the agentswhich effect it. For a general review of phosphorylation see Slotin,Synthesis, 737 (1977).

Three types of P(+5) phosphorylating agents have generally been employedin Step 2a:

    ______________________________________                                        Type I  (RO).sub.2 --P(═O)-X;                                             Type II (RO).sub.2 --P(═O)--OH or salt thereof; and                       Type III                                                                              (RNH).sub.2 --P(═O)-X or RCONH-- P(═O)(OH)(O.sup.-);          ______________________________________                                    

wherein R=phosphorus protecting groups and X=halogen.

The conversion of hydroxyl groups to phosphate monoesters generally hasbeen accomplished by the action of a phosphorylating agent of Type I.One problem with most of the Type I agents is that phosphorylatingagents which contain phosphorus(+5) atoms are not sufficiently reactiveto efficiently polyphosphorylate partially protected inositols.Monophosphorylation of 1,2,3,5,6-pentabenzylinositol with the classicalphosphorylating agent, diphenyl chlorophosphate (Type I, wherein R=C₆ H₅and X=Cl), for example, affords only a 70% yield of the desired inositoldiphenyl monophosphate (Billington et al., J. Chem. Soc., 314 (1987)).Polyphosphorylations, i.e., bis-, tris-, tetrakis-, etc., are difficultto achieve with selectivity, and separation of the many undesiredphosphorylated side products from the desired phosphorylated productproduced via this reaction scheme presents a difficult task. Forcingconditions, such as higher temperatures are problematic since thesephosphorylating agents tend to decompose, as described in Krylova etal., J. Org. Chem. USSR, 16: 277-282 (1980), or effect premature removalof hydroxyl protecting groups, discussed in Krylova et al., Zh. Org.Khim., 42: 702 (1972).

The Type II phosphorylating agents are used in situ after having beenconverted to a mixed anhydride with an activating agent such astriisopropylbenzenesulfonyl chloride or dicyclohexylcarbodiimide.However, none of these reagents are any more reactive than the Type Ireagents, and thus are equally inefficient at phosphorylating inositols.For example, inositol has been converted to a mixture of pentakis- andhexakis(phosphates) by heating in polyphosphoric acid at 120° C., asdescribed by Cosgrove, J. Sci. Food Agric., 17: 550 (1966).

An equally significant disadvantage of the aforementioned Type I andType II phosphorylating agents is that they have the potential to formcyclic phosphates when the substrate to be phosphorylated containsunprotected vicinal hydroxyl groups, especially cis vicinal hydroxylgroups. For example, when treated with diphenyl chlorophosphate,1,2:5,6-di-O-iso-propylidiene-(-)-inositol (a trans vicinal diol) and1,4,5,6-tetra-O-acetyl-myo-inositol (a cis vicinal diol) afford cyclicmonophosphates instead of the desired 3,4-and 2,3-bis(phosphates)(Angyal et al., J. Chem. Soc., 4122 (1961)). Although somebis(phosphates) can be prepared from the trans vicinal diols usingdiphenyl chlorophosphate, precautions must generally be taken withinositol phosphate triesters intermediates because they areexceptionally prone to cyclization onto a neighboring free hydroxylgroup. For example, Billington et al., J. Chem. Soc., 314 (1987), findthat 2,3,4,5,6-pentabenzyl-myo-inositol-1-(diphenyl phosphate) isdeprotected by hydrogenolysis to a mixture of myo-inositol 1- and2-phosphates. Migration of phosphate occurs because the benzyl etherprotecting groups are removed more rapidly than the phosphorusprotecting groups. Intermediate phosphate triesters with a free2-hydroxyl group cyclize and then ring open to form the reported mixtureof products.

The above cyclization and migration problems lead to the development ofa third type of P(+5) phosphorylating agent, Type III, shown above. Inthis type of agent, one or two of the phosphorus oxygens are replaced bynitrogens. The phosphorylated products, i.e., inositol phosphoramidatesor phosphorodiamidates, produced by this type of agent are apparentlynot as prone to cyclization as are the phosphorus triesters, probablybecause nitrogen is a poorer leaving group than oxygen. Angyal et al.,Aust. J. Chem., 22: 391-404 (1969) reported obtaining a mixture oftetra- and the desired pentaphosphorylated products when attempting toexhaustively phosphorylate 1-O-benzyl-myo-inositol it with themonotriethylammonium salt of N-benzoyl-phosphoramidic acid indimethylformamide (DMF) at 140° for 24 h. In this case, the phosphorusprotecting groups (including removal of the nitrogen) and pyrophosphateintermediates were hydrolyzed with hydrochloric acid. Krylova, J. Org.Chem USSR, 16: 277 (1980), reports that phosphorylation of1,2-O-cyclohexylidiene-3,6-di-O-benzyl-myo-inositol with"dianilidophosphoric chloride" afforded the desired4,5-bis(phosphordiamidite). Dianilidophosphoric chloride appears to beabout as reactive as the corresponding oxygen analog diphenylphosphorochloridate. These nitrogen-containing phosphorus protectinggroups can be removed by hydrolysis with aqueous hydrochloric acid orbuffered nitrous acid. The former method has the potential to causemigration of phosphate groups and the highest yield reported for thelatter method is 25% . These Type III phosphorylation agents, therefore,while offering hope of obtaining polyphosphates from a variety ofprotected inositols, have a number of unresolved problems associatedwith their use.

The first total synthesis of inositol 1,4,5-tris(phosphate) was reportedby Ozaki et al., Tetrahedron Lett., 27: 3157-3160 (1986). This synthesisillustrates the weaknesses of the best existing technology when appliedto a synthetically difficult, biologically important molecule. Ten stepsof chemistry were required to prepare (+)-2,3,6-tri- benzylinositol, anappropriate precursor for phosphorylation. Tris(phosphorylation) waseffected by means of dianilidochlorophosphate in "ca. 41% yield". Theauthors noted that "[a]t the present time, phosphorylation andsubsequent deblocking reaction[sic reactions] [using isoamyl nitrite]are not satisfactory". No overall yield of final product was given. Gigget al., Carbohydrate Res., 140: cl (1985)) also reported a longsynthesis of the same tribenzylinositol, but they have apparently beenunable to obtain the desired tris(phosphate) from this precursor.

In conclusion, the regioselective synthesis of many inositol phosphatesby means of the existing P(+5) technology is a long, risky andinefficient process.

Over the past decade, phosphorylation with phosphorus(+3) (P(+3))phosphorylating agents (also known as phosphitylating agents) hasrevolutionized the field of oligonucleotide synthesis. Firstchlorophosphite diesters, developed by Letsinger et al., J. Am. Chem.Soc., 97: 3278 (1975), and then more recently phosphoramidites,developed by Beaucage et al., Tetrahedron Lett., 22: 1859 (1981), havebeen the reagents of choice for the construction of phosphorus diester,as opposed to monoester, bonds in oligonucleotides. The use ofphosphorus(+3) reagents for the construction of phosphorus diestersrequires that two key hydroxyl groups become attached to a monoprotectedphosphitylating agent. Adapting phosphorus(+3) methodology to thepreparation of phosphorus monoesters requires that one key hydroxylgroup become attached to a phosphitylating agent with two protectinggroups.

There are scattered reports in the literature on methods for preparingphosphate monoesters by means of phosphitylation agents. Many of thesereports, however, involve the use of phosphitylating agents designed formaking phosphate diesters and one would anticipate that these agentswould produce cyclic phosphite esters from many inositol substrates.Bannwarth et al., Helv. Chim. Acta, 70: 175-186 (1987), report acomprehensive study on appropriate phosphitylating agents for makingphosphate monoesters. Kozlova et al., J. Gen. Chem. USSR, 39: 2403-2406(1969), disclose the only example of phosphitylation of a cyclitolderivative. These authors, however, were interested in the preparationof phosphate diesters of inositol, that is, phospholipids. Consequently,the phosphitylating agent they chose to use (the mixed anhydride from0-benzylphosphorous acid and O,O-diphenylphosphoric acid) is one whichmight be anticipated to produce cyclic phosphite esters with many of theinositol substrates of interest to this invention. Since all of theother hydroxyl groups in the inositol substrate they used wereprotected, they observed no cyclization and obtained an inositol (mono-)phosphite diester as the major product. No phosphite triesters ofinositol are known.

The present invention centers around the creation of a superior processthat uses phosphitylation as a key step in the preparation of cyclitolphosphates, particularly inositol phosphates. Prior to the studiesdisclosed herein, no one had used phosphitylation to prepare cyclitolphosphate monoesters nor had anyone used phosphitylation to attach morethan one phosphorus to cyclitols. The general usefulness ofphosphitylation for the preparation of poly(phosphates) from startingmaterials with more than one hydroxyl group did not appear to have beenestablished. In particular, there was no evidence demonstrating thatchanging to methods based on phosphitylation would alleviate the sidereactions which interfere with more conventional phosphorylating agents,i.e., incomplete poly-(phosphorylation), cyclization, and phosphatemigration.

Although the phosphitylating agents used in the present process havebeen employed in other systems, they have never been applied to theproblem of producing inositol phosphates and other cyclitol phosphates,and indeed, their ability to effectively work in the present system andavoid many of the problems prevalent in the art processes is quitesurprising.

SUMMARY OF THE INVENTION

The present invention involves a process for regioselectively producingcyclitol phosphates comprising reacting an optionally protected cyclitolwith, in order of (a) through (c), (a) a bis-protected phosphitylatingagent, (b) an oxidizing agent, and (c) a phosphorus deprotecting agent,and, if necessary (as is usually the case), a hydroxyl deprotectingagent. The preferred process produces an inositol phosphate, mostpreferably a myo-inositol poly(phosphate) such as the1,3,4,5-tetrakis(phosphate) and the 1,4,5-tris(phosphate).

DETAILED DESCRIPTION OF THE INVENTION

The chemical process of this invention is directed primarily towards thesynthesis of certain isomers of myo-inositol poly(phosphates), but thisprocess is applicable to the regioselective synthesis of all inositolphosphates and more generally to the regioselective synthesis of anycyclitol phosphate. For simplicity sake, the methodology of thisinvention is illustrated in detail only for myo-inositolpoly(phosphates).

The overall process of the present invention as illustrated by Scheme Irelies on a superior, three-step method for phosphorylation, i.e., (a)phosphitylation followed by (b) oxidation, and then by (c) deprotectionIn certain circumstances, it may be desirable to and an additional step,hydroxyl group protection, following step (a) and prior to step (b).##STR1##

It should be noted that in conventional nomenclature, the three adjacentsyn hydroxyl groups of myo-inositol are a]ways designated as occupyingthe 1, 2, and 3 positions. Since myo-inositol possesses a plane ofsymmetry (i.e., it is a meso isomer), the 1 and 3 positions and the 4and 6 positions are identical. When one of these positions is modified,two enantiomers are possible and the nomenclature for these compoundscan become confusing For example, the name 1(R)-myo-inositol phosphaterepresents the same molecule as 3(S)-myo-inositol phosphate. Thus, forclarity, all synthetic intermediates are referred to herein by thenumbering system of the desired final product. The IUPAC-approved name(European J. Biochemistry, -5: 1-12 (1968)), if different from theaforementioned nomenclature, will also be provided using brackets "{}".As an example of the numbering system employed herein, an intermediatein the synthesis of myo-inositol 1,2,4,5-tetrakis(phosphate) withhenzoates at the positions that will eventually become the 3- and6-hydroxyl groups shall always be referred to as a 3,6 -dibenzoate. TheIUPAC nomenclature {1,4-dibenzoate} will appear as appropriate.

Throughout the specification, the term "phosphitylation" is defined as areaction between a free hydroxyl group on a cyclitol, or moreparticularly an inositol compound, and a bis-protected electrophilicphosphorus species which has a phosphorus in the (+3) oxidation state,P(+3), termed a "phosphitylating agent". The product of this process isa cyclitol or inositol phosphite ester, having a P(+3) phosphorus group.Phosphitylation followed by oxidation results in a net"phosphorylation", which means that the phosphorus in the phosphorylatedcompound is converted to the (+5) oxidation state, P(+5), as part of aphosphate monoester group.

As used herein "cyclitol phosphates" or "inositol phosphates" denotethose phosphorylated derivatives of cyclitols or inositols which haveone or more hydroxyl groups converted to phosphate monoesters. Acyclitol polyphosphate or inositol polyphosphate has more than onehydroxyl group converted to phosphate monoesters.

Phosphitylation is used in the process of the present invention for"regioselectively" preparing inositol phosphates. The term"regioselectively" denotes that a preselected number of phosphorusgroups are attached to preselected oxygens of inositol. In accordancewith the invention, regioselectivity is achieved by one or both of thefollowing means: (i) selecting an inositol starting material which hasprotecting groups on all oxygens which are not phosphorylated in thedesired final product, that is, those oxygens in the final product thatare hydroxyl groups and not phosphate monoesters, or (ii) by limitingthe phosphitylating reaction by reducing the amount of phosphitylatingagent, the reaction time, the reaction temperature or any combinationsthereof. The latter means (ii) of achieving regioselectivity is hereinreferred to as "limited" phosphitylation. Limited phosphitylation takesadvantage of the intrinsic differences in reactivity of the inositoloxygens, particularily the lower intrinsic reactivity of the 2-positionhydroxyl oxygen. In contrast, when regioselectivity is achieved by means(i), an excess of phosphitylating agent is used for a period long enoughto completely phosphitylate all of the unprotected hydroxyl groups. Inthis case, the term "exhaustive" phosphitylation is employed herein.

One or more hydroxyl groups on the starting material may, as is usuallydesired, be "protected" by one or more "protecting groups", and the term"protected hydroxyl group" indicates this type of protected species.During phosphitylation reactions of the type described herein, protectedhydroxyl groups do not react with the phosphitylating agent The conceptof using protecting groups to mask reactive functional groups is wellunderstood in the field of synthetic chemistry and is discussed atlength, for example, in Green, Protective Groups in Organic Synthesis,John Wiley & Sons, N. Y. (1981).

Which starting material hydroxyl groups should be protected depends uponthe ultimate product desired. The concept that one skilled in the artcan prepare an inositol starting material with the appropriate number (0to 5) and types of protecting groups located on preselected hydroxylgroups is denoted by the terminology "optionally protected". As part ofthis invention, it has also been discovered that in the case where thehydroxyl group in the 2-position and several other hydroxyl groups areunprotected, the lower reactivity of the 2-hydroxyl group can be takenadvantage of to obtain regioselectively phosphitylated products.

Suitable protecting groups for the hydroxyl groups of the cyclitolcompounds include, but are not limited to, ethers, silyl ethers, esters,orthoesters, carbonates, cyclic acetals, cyclic ketals, cyclicorthoesters, and cyclic carbonates. Preferred protecting groups includebenzyl ethers, benzoate esters and cyclohexylidene ketals.

Phosphitylation, the first and key step in the present process, iscarried out by a phosphitylating agent. The phosphitylating agents usedherein are "protected" by two "protecting groups", and the term"bis-protected phosphitylating agent" denotes such as species.Protecting groups on the phosphorus species are referred to herein as"phosphorus protecting group(s)". Phosphitylating agents suitable forthe present invention include, but are not limited to, compounds of theformula ##STR2## wherein

X is selected from the group consisting of a halogen, i.e., F, Cl, Br orI, NR₂ ², where R² is aryl or a C₁ -C₁₅ straight chain, branched orcyclic alkyl where the alkyl may be internally interrupted by etheroxygen, and OH or a salt thereof;

Y and Z, independently, are selected from the group consisting of

O,

S,

NH, and

NR² ;

R and R¹, independently, are phosphorus protecting groups. Suitablephosphorus protecting groups include, but are not limited to,

aryl, and

a C₁ -C₁₅ straight chain, branched or cyclic alkyl,

where the alkyl may be internally interrupted with ether oxygen andwhere aryl or the alkyl may be substituted or unsubstituted with nitro,sulfonyl, halogen ester and ketone groups; provided that

when Y or Z, single or in combination, are O, then the group attached toO, that is, R and R¹, must be CH₃, CH₂ CC1₃ CCBr₃ aryl, CH₂ --aryl, CR₂² CC1₃, CR₂ ² CBr₂ ²,CCl₃, CR₂ ² CBr₃, CH₂ CH₂ --A, wherein A is a groupwhich will stabilize an adjacent carbanion such as a nitrile, asulfonyl, or an electron-deficient aryl group such as p-nitrophenyl.Other suitable phosphorus protecting groups are known in the art.

In the above formula, X is preferably a halogen or NR₂ ². When X is ahalogen, most preferably it is Cl. The is NR₂ ², most preferably it isdiisopropylamino or 1-morpholinogroup. Y and Z in the formula arepreferably both O and when Y and Z are both O, R and R¹ : are preferablyboth CH₃. The most preferred phosphitylating agent of the above formulais dimethyl chlorophosphite, that is where X is Cl, Y and Z are both O,and R and R¹ are both CH₃.

When the phosphitylating agent is a phosphoramidite (i.e., X is NR₂), aweak acid such as tetrazole is added to activate the agent When thephosphitylating agent is a phosphorous acid diester (i.e., X is OH) or asalt thereof, the agent must be activated by a reagent capable ofconverting the phosphorus acid to a mixed anhydride. Examples of suchreagents are triisopropylbenzenesulfonyl chloride anddicyclohexylcarbodiimide.

When the phosphitylating agent is a halophosphite or a phosphorous acid,about 1.0 to 2.0 equivalents of an acid scavenger per equivalent ofphosphitylating agent is preferably added. In other cases an acidscavenger is optional. The preferred acid scavengers are low molecularweight, non-nucleophilic, tertiary amines. The most preferred acidscavenger is diisopropylethylamine. Heterocyclic amines such as pyridineand N-methylimidazole are used to catalyze reactions similar tophosphitylation. These heterocyclic amines can also be used in thephosphitylation reactions of this invention.

The phosphitylating agents described above are used to effect exhaustiveor limited phosphitylation of optionally protected inositols. An inertsolvent is employed in the reaction. Suitable solvents includehalocarbons, ethers, esters, and polar aprotic solvents such asdimethylformamide, acetonitrile, pyridine and dimethylsulfoxide. Itshould be noted that a suitable solvent does not have to be one that hasthe ability to completely dissolve the inositol starting material, butit is preferably one which affords a homogeneous reaction mixture atsome point during the phosphitylation reaction.

In the case of exhaustive phosphitylation to produce phosphite esters,the quantity of phosphitylating agent and the reaction conditions areadjusted so that no unprotected hydroxyl groups remain unphosphitylatedwhen the reaction is halted. Exhaustive phosphitylation is effected byadding 1.0 to about 2.5 equivalents of phosphitylating agent perunprotected hydroxyl group. The phosphitylation can be performed atabout -80° to 50° and for about 5 min to 24 h. Preferred reactionconditions are about 0 to about 20° for about 1h. The preferred solventsinclude dichloromethane. Dichloromethane is generally the most preferredsolvent because removal of water soluble by-products is easier when thereaction is complete. However, when the optionally protected inositolstarting materials are unusually insoluble, dimethylformamide is themost preferred solvent.

In the case of limited phosphitylation to produce phosphite esters,either or both the quantity of phosphitylating agent and the reactionconditions are adjusted so that some of the unprotected hydroxyl groupsremain unphosphitylated when the reaction is halted. This is usuallydone by limiting the amount of phosphitylating agent to about 1.0 to 1.2equivalents per hydroxyl group to be phosphitylated. The phosphitylatingagent is preferably added to a solution of this precursor at about -70°to about -40°. The reaction is allowed to proceed within thistemperature range for about 1 to about 24 h and then the reaction isslowly warmed to about 0°. For limited phosphitylation, the solventpreferably employed is able to completely dissolve the optionallyprotected inositol precursor. The preferred solvent isdimethylformamide. In the preferred version of limited phosphitylation,the unreacted hydroxyl groups are protected in situ with a hydroxylprotecting group before oxidation. Protection of the unreacted hydroxylgroups ensures that the phosphorus groups regioselectively introducedduring limited phosphitylation do not migrate to neighboring freehydroxyl groups later in the synthesis. If this hydroxyl protecting stepis omitted, inositol poly(phosphates) with lower isomeric purity will beproduced. The preferred hydroxyl protecting groups used are esters, mostpreferably an acetate. Protection of the hydroxyl groups viaesterfication is preferably performed with an acid chloride in thepresence of a catalyst. The most preferred catalyst isdimethylaminopyridine.

In the situation where one desires to phosphorylate all of theunprotected hydroxyl groups in an inositol compound except for anunprotected 2-hydroxyl group, the limited phosphorylation processdescribed herein has been found to be surprisingly regioselective.Example 2, Step 1, describes a reaction in which three of four possiblehydroxyl groups are phosphitylated. After oxidation, the only productsdetected are the desired tris(phosphate) and 5-10% oftetrakis(phosphate).

Following either exhaustive or limited phosphitylation the resultingphosphite esters are preferably not isolated. Oxidation to phosphateesters is performed with oxidizing agents such as peroxides, periodate,halogens and other halogenating agents (in the presence of water),oxygen, permanganate, chromate, iodobenzene diacetate, ozone,hypohalites, persulfate, ruthenium tetraoxide, etc. The most preferredoxidizing agents are hydrogen peroxide and meta-chloroperoxybenzoicacid. These oxidants are preferably used at about 0° to about 20°,preferably after adding a neutral aqueous buffer to quench any excessphosphitylating agent. The resulting phosphate esters are isolated byallowing (or causing, by addition of a poor solvent) them to precipitatefrom the reaction mixture. Alternatively, partitioning between aqueousand organic solvent affords a crude product which is optionally purifiedby chromatography or crystallization.

The protecting groups on the hydroxyl groups and the phosphorus groupsare subsequently removed by, respectively, standard "hydroxyldeprotecting agents" and "phosphorus deprotecting agents". The preferredorder of deprotection involves selective phosphorus deprotectionfollowed by hydroxyl group deprotection. Reversing the order ofdeprotection, or simultaneous deprotection, is possible, but not usuallypreferred since the intermediate phosphate esters can cyclize. When thishappens, the product will generally be an isometric mixture of inositolpoly(phosphates).

Suitable hydroxyl and phosphorus deprotecting agents will be readilyapparent to those skilled in the art and exemplary agents are discussedbelow.

With respect to phosphorus deprotecting agents, in the situation where Yand/or Z of the phosphitylating agents are sulfur, for example, thephophorus protecting groups are removed by oxidative hydrolysis, such aswith iodine in the presence of aqueous buffer as described by Takaku etal., Tetrahedron Lett., pp. 411-414 (1972).

Where Y and/or Z are NR², the phosphorus protecting groups can beremoved with aqueous mineral acid. When Y and/or Z are NH, eithermineral acid or buffered nitrous acid can be used. In either case, whenphosphorus is still in the +3 oxidation state, these labile nitrogenprotecting groups can be easily converted to phosphite esters bytreatment with an acid and an alcohol respectively.

Finally, in the situation where Y and/or Z are O, the suitablephosphorus protecting groups depend upon the nature of R and R¹. TableI, below, provides some examples of phosphorus deprotecting agents.

                  TABLE I                                                         ______________________________________                                        R and R.sup.1 Phosphate Deprotecting Agents                                   ______________________________________                                        --CH.sub.3    [TMSBr or HBr]                                                  --CH.sub.2 --CBr.sub.3                                                                      [Zn/HOAc]                                                       --CH.sub.2 --CCl.sub.3                                                                      [Zn/HOAc]                                                       Aryl          [H.sub.2, Pd/C]                                                 --CH.sub.2 -Aryl                                                                            [H.sub.2, Pd/C]                                                 9-fluorenylmethyl                                                                           [NH.sub.4 OH]                                                   --CH.sub.2 --CH.sub.2 -Q,                                                                   [DBU]                                                           ______________________________________                                    

wherein Q is a group which will stabilize an adjacent carbanion such asa nitrile, sulfonyl, or an electron-deficient aryl group (i.e.p-nitrophenyl).

Methyl protecting groups on the most preferred phosphitylating agent,dimethyl chlorophosphite (Y and Z are O, and R and R¹ are CH₃), arepreferably removed with bromotrimethysilane in an inert solvent such asdichloromethane or hydrobromic acid in anhydrous acetic acid. Otherreagents which can remove these methyl esters include: other anhydrousacids with nucleophilic conjugate bases (such as hydroidic acid),oxygenophilic Lewis acids with nucleophilic ligands (such asiodotrimethylsilane and boron tribromide), and hard Lewis acids in thepresence of soft nucleophiles (such as boron trifluoride/propanethiol).When an acid-labile hydroxyl protecting group such as cyclohexylidene ispresent, bromotrimethysilane is the most preferred. agent, since it isthe most chemoselective. A second advantage of bromotrimethylsilane isthat deprotection with this reagent is actually a two step process.First, treatment of an inositol poly(dimethyl phosphate) with thisreagent initially produces an inositolpoly(bis(trimethylsilyl)phosphate) and this intermediate spontaneouslyhydrolyzes to a deprotected phosphate monoester on contact with water.Other deprotection methods frequently generate inositol poly(dihydrogenphosphates) which (as moderately strong acids) may be unstable. A thirdadvantage of bromotrimethylsilane is that if premature deprotection ofhydroxyl protecting group(s) has occurred, this reagent will temporarilyprotect them as silyl ethers. When the hydroxyl protecting groups arebenzoates, premature removal of these protecting groups is not a problemand hydrobromic acid is the most preferred agent for its convenience.After removal of either of these volatile reagents the resultinginositol poly(dihydrogen phosphates) can be isolated by precipitation asa salt or simply used directly in the next reaction. It should be notedthat standard methods (i.e., aqueous ammonia used in oligonucleotidesynthesis) for removing the methyl protecting groups from phosphoruswill not work here.

A more complete discussion of phosphorus deprotection can be found inSonveaux, Bioorganic Chemistry, 14: 274-325 (1986) and the referencesdiscussed therein.

As noted above, the hydroxyl protecting groups, which include thosepresent in the optionally protected inositol starting materials and anyhydroxyl protecting groups added in the limited phosphorylation process,are generally removed last Suitable hydroxyl deprotecting agents includeaqueous hydroxide, most preferably aqueous potassium hydroxide. Green,"Protective Groups in Organic Synthesis", John Wiley & Sons, N.Y. (1981)provides other examples of suitable hydroxyl deprotecting agents.

The Examples that follow contain procedures for preparing two noveloptionally protected inositol starting materials,3,6-dibenzoyl-myo-inositol and 2,6-dibenzoyl-myo-inositol, which areuseful, respectively, for preparing the naturally occurring secondmessengers myo-inositol 1,4,5-tris(phosphate) and myo-inositol1,3,4,5-tetrakis(phosphate). Schemes 4 and 3, respectively, depict thesynthesis process of these compounds. The preparation of two isomers ofthese natural compounds, myo-inositol 1,2,4,5 tetrakis(phosphate)myo-inositol 1,4,5,6 tetrakis(phosphate), is also described in theExamples. Schemes 2 and 5, respectively, depict the synthesis process ofthese compounds. Many of the other optionally protected inositols andother cyclitols contemplated as starting materials in the presentprocess are obtainable through known synthesis procedures. ##STR3##

The list of compounds given below in Table II includes a few additionalavailable starting materials organized by final product which may beobtained therefrom in accordance with the present invention. This listis not intended to be all inclusive.

                  TABLE II                                                        ______________________________________                                        Product     Inositol                                                          (inositol phoshate)                                                                       Derivative         Reference                                      ______________________________________                                        1,2,3,4,5,6-hexakis-                                                                      (inositol)                                                        1,2,3,4,5-pentakis-                                                                       6-benzyl-          A                                                          {4-benzyl-}                                                       1,2,4,5,6-pentakis-                                                                       3-benzyl-          A                                                          {1-benzyl-}                                                       1,2,3,4,6-pentakis-                                                                       5-benzyl-          A                                              1,2,4-tris- 3,6-diallyl-5-benzyl-                                                                            B                                                          {1,4,-diallyl-5-benzyl-}                                          1,2,5-tris- 3,6-diallyl=4-benzyl-                                                                            B                                                          {1,4,-diallyl-6-benzyl-}                                          1,2-bis-    1,4,5,6-tetrabenzyl-                                                                             C                                              1,4-bis-    2,3:5,6-diisopropylidene-                                                                        D                                                          {1,2:4,5-diisopropylidene-}                                       1,6-bis-    2,3:4,5-dicyclohexylidene-                                                                       E                                                          {1,2,5,6-dicyclohexylidene-}                                      4,5-bis-    1,2:3,4-dicyclohexylidene-                                                                       E                                              ______________________________________                                         References:                                                                   A Garegg et al., Carbohydrate Res., 130: 322 (1984).                          B Gigg et al., Carbohydrate Res., 140 c1-c3 (1985).                           C Angyal et al., J. Chem. Soc., 6949 (1965).                                  D Gigg et al., Carbohydrate Res., 142: 132-134 (1985).                        E Angyal et al., J. Chem. Soc., 4116 (1961).                             

Optionally protected starting materials suitable for the preparation ofall of the 63 possible isomers (including enantiomers) of myo-inositolmono-and poly(phosphates) are available using conventional synthetictechniques. For example, an inositol starting material with all sixhydroxyl groups differentiated might be prepared as described below andshown in Scheme 6. Both enantiomers of4-O-benzyl-1,6:2,3-di-O-cyclohexylidene-myo-inositol are first preparedin pure form as described by Garegg et al., Carbohydrate Res., 139:209-215 (1985). The remaining 5-hydroxyl can be protected and the lessstable, trans-fused 1,6-ketal can be selectively hydrolyzed. (Angyal etal., J. Chem. Soc., 4116 (1961) describe a similar selective hydrolysis.Klyashchitskii et al., Zh. Org. Khim., 7: 492 (1971) report that ininositol derivatives similar to diol 18 differentiation between the 1-and 6-hydroxyl groups is possible since the 1-hydroxyl group is hinderedby being on the endo face of this cis-fused ring system. Once the 1 and6 positions are differentiated, the remaining ketal can be removed. Theaxial 2-hydroxyl group is known to be much less reactive than any of theother hydroxyl groups, thus these hydroxyl groups in diol 21 can also bedifferentiated. For this process protecting groups R^(a) through R^(e),can be either: permanent hydroxyl protecting groups or temporaryhydroxyl protecting groups. In this context, "temporary" protectinggroups are those which are removed prior to phosphitylation whereas"permanent" protecting groups remain. The synthesis of2,3,6-tribenzylinositol as reported in Osaki et al., Tetrahedron Lett.,27: 3157-3160 (1986) was carried out using a similar strategy. While theabove route generally will not be the most efficient one for preparingan optionally protected inositol, this route demonstrates that synthesisof appropriate starting materials for any myo-inositol phosphate ispossible. ##STR4##

As part of this invention, a novel and convenient method was developedfor preparing starting materials suitable for the synthesis of thebiologically important molecule myo-inositol1 1,3,4,5-tetrakis(phosphate). An optionally protected inositol starting material for theabove synthesis has protecting groups on the 2- and 6-hydroxyl groups{2- and 4-hydroxyl groups}. Since the hydroxyl groups of inositol aremost easily differentiated by means of cyclic ketals, such startingmaterials are not readily available and indeed have never been reported.One object of this invention is a convenient process for the preparationof 2,6-diacylated inositols {2,4-diacylated inositols}. The known2,3:4,5- {1,2:5,6-} and 1,2:4,5-bisketals of inositol, reported byGaregg, Carbohydrate Res., 130: 322 (1984) and Gigg et al., CarbohydrateRes., 142: 132 (1985), are acylated and the ketal groups are hydrolyzed.The resulting 1,6- or 3,6-{1,4}-diacylinositol is isomerized by means ofa basic catalyst to a mixture 1,6-, 2,6- {2,4}, and 3,6- {1,4}diacylinositol. Acyl groups preferred for this process are those whichhydrolyze slowly and the substrate preferred is 3,6-{1,4}dibenzoylinositol. Acyl migration is effected by means of a basiccatalyst such as a tertiary amine (e.g., triethylamine), sodiumhydroxide, potassium t-butoxide, sodium hydride, or sodium acetate. Thepreferred catalysts are non-nucleophilic (e.g., tertiary amine,potassium t-butoxide or sodium hydride). The more preferred catalystsare weakly-basic (e.g., pyridine or sodium acetate). The most preferredcatalyst is pyridine. A solvent containing some water is preferred andaqueous pyridine is the most preferred solvent. A reaction time andtemperature compatible with the concentration and strength of the basiccatalyst is used. In the most preferred reaction medium (6:4pyridine-water), the reaction is performed at temperatures from about 0°to 100° and for times of about 10 min to 20 days. Reaction for 1 h at100° is the most preferred. The mixture of isomers can be separated by aprecipitation, fractional crystallization, and/or chromatography. Themost preferred method is to add water or an alcohol to the mostpreferred reaction mixture to precipitate the 3,6-dibenzoate{1,4-dibenzoate} and then isolate the 2,6-dibenzoate {2,4-dibenzoate} byfractional crystallization from a second solvent such as dichloromethaneor water.

The practicality of the above process is surprising for several reasons.First, separation of these three isomers is remarkably easy. Second, thereview of the chemistry of myo-inositol by Shvets, Russian Chem. Rev.,43: 488 (1974)) states on page 492 that acetyl migration "is almostequally probable in trans- and cis- directions." This implies that thebasic conditions needed to generate the desired 2,6-{2,4 } isomer shouldproduce all 15 possible diacyl isomers.

The methods disclosed herein provide a novel and superior process forregioselectively preparing inositol phosphates. In particular, thesemethods, which are based on phosphitylating agents, have the followingadvantages over conventional P(+5) phosphorylating agents. First,phosphitylating agents are intrinsically more reactive thanphosphorylating agents. Phosphitylation followed by oxidation thereforegenerally affords higher yields of purer products than directphosphorylation, especially when more than one phosphorus is attached toan inositol. Second, the preferred phosphitylating agents show notendency to produce cyclic phosphites. Third, using this process,phosphorus migration can be avoided. Finally, limited phosphitylationappears to be more regioselective and useful than limitedphosphorylation, and use of limited phosphitylation can greatly simplifythe preparation of optionally protected inositol starting materials forsynthesis of inositol phosphates which lack a 2-phosphate group.

Many of the intermediates prepared by the process described herein havenever been synthesized before. For instance, no examples of inositolphosphites, inositol tris(phosphates), and inositol tetrakis(phosphates)in which all phosphorus groups are esterified have been reported. Asidefrom their utility as intermediates for the preparation of inositolphosphates, these families of compounds could serve as medicinallyuseful prodrugs. Intracellular hydrolysis of the esters which block thephosphate groups would result in release of the naturally-occurringinositol phosphate second messengers or analogs thereof.

By means of the process of this invention, suitable quantities ofcylitol phosphates, especially myo-inositol phosphates, can be preparedin isomerically-pure form. Synthetically prepared, naturally occurringinositol phosphates and analogs and isomers thereof can be used inresearch on biological and medicinal phenomena associated with thesesecond messengers. In particular, compounds prepared by means of thisinvention can be used as starting materials for the preparation ofradioactively-labeled inositol phosphates. For example, Angyal et al.,Aust. J. Chem., 20: 2647-2653 (1967) describe a method for tritiatinginositols using tritiated water and a platinum oxide catalyst. Theisomers and analogs of the natural second messengers made available bymeans of the present invention are candidates as agonists andantagonists.

General Methods

Unless otherwise stated, all inositol derivatives are racemates. Unlessotherwise stated, all parts and percentages are by weight and alltemperatures are in degrees Celsius. Compounds in the Examples arereferred to by underlined numbers

NMR spectra were obtained on GE 300 MHz or Bruker 360 MHz instruments.Unless otherwise stated, spectra were determined in deuterochloroformand chemical shifts were calculated relative to internal tetramethylsilane Spectra of aqueous samples were referred to water set at 4.80ppm. Coupling constants (J) are reported in Hz.

Thin Layer Chromatography (TLC) was carried out on 2.5×7.5 cm silica gelplates with fluorescent binder (Whatman, Maidstone, England). SolventA=85:15:1 chloroform-methanol-water (volume/volume) was used.

1,2:4,5-Diisopropylidene-3,6-dibenzoyl-myo-inositol (1) and3,4-isopropylidene myo-inositol (24) were prepared as described by Gigget al., Carbohydrate Research, 142: 132 (1985). Dimethyl chlorophosphitewas prepared as described by Mazour, U.S. Pat. No. 4,079,103 (1978).

High Pressure Liquid Chromatography (HPLC) was performed on a Mono Q(Pharmacia, Uppsala) anion exchange column. Buffer "A" contained 50 mMHEPES and was at pH 7.4; Buffer "B" contained 250 mM sodium sulfate and10 mM HEPES, and was at pH 7.4. Both buffers also contained 1 mM MgSO4,0.1 mM ZnSO4 and 0.1 mM EDTA. A gradient of 5% B to 90% B in 30 min wasused. The flow rate was 1 mL/min. Detection was by absorbance at 240 nm(inositol benzoates) or the on-line enzymatic system for detection ofphosphomonoesters of Meek, Proc NatI. Acad. Sci., 83: 4162, (1986).

EXAMPLE 1 - PREPARATION OF LITHIUMMYO-INOSITOL-l,2,4,5-TETRAKIS(PHOSPHATE) (6)

Step 1 Preparation of 3,6-dibenzoyl-myo-inositol{1,4-dibenzoyl-myo-inositol} (2)

A solution of 20 g (42.3 mmol) of bisacetonide 1 in 300 mL of beilingchloroform was hydrolysed by the addition of 30 mL trifluoroacetic acidand 3 mL of water. The mixture was refluxed until the reaction wascomplete according to TLC (about 30 min). Product began to precipitateafter 5 min. After the mixture had cooled, collecting and drying theprecipitate gave 11.8 g (71% yield) of dibenzoate 2 as a white powdermelting at 243°-246°.

TLC (Solvent A): 1 Rf=0.95; 2, 0.55; 1,2-isopropylidene-3,6-dibenzoylinositol, 0.75. ¹ H NMR (DMSO-d6) δ=7.5-8.1 (m, 10H, benzoate), 5.3 (t,J=10, 1H , H6), 5.1 (m, 4H, 4 OH), 4.8 (dd, J=2,10, 1H, H3), 4.1 (s, 1H,H2), 3.9 (t, J=10, 1H, H 4 or 5), 3.7 (dd, J=2,10, 1H, H1), 3.5 (t, J=9,1H, H4 or 5)

Step 2. Preparation of 3,6-dibenzoyl-myo-inositol1,2,4,5-tetrakis(dimethyl phosphate) (4)

A 100-mL round-bottomed flask with septum cap and magnetic stirrer barwas charged with 3.00 g (7.7 mmol) of dibenzoate 2, 12 mL of drydimethylformamide, and 14 mL (80 mmol, 10.4 eq) of drydiisopropylethylamine (Aldrich, Milwaukee, WI; distilled from calciumhydride). Dimethyl chlorophosphite (7.6 mL, 70 mmol, 9 1 eq) was addedslowly at room temperature. After 15 min the mixture was cooled on iceand 12 mL of 0.5M pH 7 sodium phosphate buffer and 12 mL (about 100mmol, 14 eq) of 30% hydrogen peroxide were added. After standingovernight at 0° , the resulting precipitate was collected, washed withwater, air dried, and washed with ether to give 4.2 g, (73% yield) oftetrakis(phosphate) 4 as a crystalline powder.

TLC (Solvent A): Rf=0.66.

H1-decoupled ³¹ P NMR: δ=1.68, 2.03, 2.17 and 2.74 ppm. ¹ H-NMR:δ=7.2-7.8 ppm (m, 10 H benzoate), 5.9 (t, 1H, H2): 5.2-5.4 (m,3H); 4.9(m, 2H); 3.2-4.8 (m 24H, OCH₃). Material from a similar preparationmelted at 211-213° . Step 3. Preparation of lithium3,6-dibenzoyl-myo-inositol 1,2,4,5-tetrakis(phosphate) (5)

A solution of 2.20 g (2.68 mmol) of tetrakis(dimethyl phosphate) 4 in 20mL of 30% hydrogen bromide in acetic acid (Aldrich) was heated at 60°for 0.5 h. The reaction mixture was concentrated on a rotary evaporator(at about 1 mm, 40° ) and the residue was co-evaporated twice withwater. The residue was dissolved in water, and the pH of the resultingsolution was adjusted to 10 with 4 M aqueous lithium hydroxide. Thebasic reaction mixture was added dropwise with vigorous stirring toethanol. After standing at 0° for 1 h, the resulting precipitate wasfiltered, and washed with ethanol and ether to yield 1.70 g of thelithium salt of tetrakis(phosphate) 5.

HPLC: With detection by UV at 240 nm, there was only a single peak. Ithad a retention time of 24 min which indicated a tetrakis(phosphate).There was no detector response with the enzymatic phosphate monoesterdetection system.

Step 4. Preparation of lithium myo-inositol-l,2,4,5-tetrakis(phosphate)(6)

A solution of 1.80 g (2.40 mmol) of dibenzoate 5 (from a preparationsimilar to step 3 above) in 5.1 mL of 1.0M aqueous lithium hydroxide washeated at 60° for 1 h. HPLC of the reaction mixture showed the completedisappearance of the UV peak due to 5, and the appearance (usingenzymatic phosphate detection) of a 9:1 mixture of two peaks withappropriate retention times for tetrakis- and tris(phosphates)respectively. The pH of the mixture was adjusted to 5 with 1.0Mhydrochloric acid. The reaction mixture was adsorbed to a 2.5 cm by 25cm Dowex 1 column, and the products were eluted with a lithium chloridegradient. Three 10 mL fractions of each of the following concentrationsof lithium chloride were collected: 0 1, 0.2, 0.3 0.4, 0.5, 0.6, 0.7 and0.8 M. The effluent fractions were checked by isocratic HPLC using amobile phase of 85 % "B" buffer Fractions from the second 0.5M fractionto the third 0.7M lithium chloride fraction contained only the desiredtetrakis(phosphate) and were combined and evaporated to near dryness.The residue was triturated with ethanol to produce a powder. The powderwas collected by filtration, and washed with ethanol and ether to give0.50 g of tetrakis(phosphate) 6. HPLC, ¹ H-NMR and ³¹ P-NMR indicatedthat this material was homogeneous. Gradient HPLC using phosphatedetection showed a single peak with a retention time of 24.1 min. ¹H-decoupled ³¹ P NMR (pH 10) δ=6.17, 6.29, 6.35, and 6.64. ¹ H NMR (pH10) δ=4.5 (d, 1H H2), 4.15 (app q, J=9, 1H, H4) 3.7-3.9 (m, 3H, H1, H5,H6) 3.5 (dd, J =2,13, 1H, H3).

EXAMPLE 2. PREPARATION OF LITHIUM MYO-INOSITOL 1,4,5-TRIS(PHOSPHATE)(15)

Step 1. Preparation of 2-acetyl-3,6-dibenzoyl-myo-inositol1,4,5-tris(dimethyl phosphate) (13)

A 50-mL, three necked flask fitted with septum cap, internal thermometerand magnetic stirrer bar was charged with 1.00 g (2.6 mmol) of3,6-dibenzoylinositol (2), 10 mL of dry dimethylformamide and 2.6 mL (15mmol, 5.8 eq) of dry diisopropylethylamine. After cooling to -40° , 0.93mL (8.6 mmol, 3.3 eq) of dimethyl chlorophosphite was added dropwise sothat the temperature remained below -40° . After 30 min at -40°, thereaction was allowed to slowly warm to room temperature. Then 25 mg(0.33 mmol, 0.13 eq) of 4-dimethylaminopyridine (Aldrich) and 0.35 mL(4.9 mmol, 1.9 eq) of acetyl chloride were added. After stirring for 30min at room temperature, 3 mL (about 26 mmol, 10 eq) of 30% hydrogenperoxide was added dropwise. The reaction mixture was allowed to standovernight at 0°. The resulting precipitate was collected, washed withwater, and vacuum dried to yield 1.19 g (61%) of impure tris(dimethylphosphate) 13. According to TLC, the desired product was contaminatedwith 5-10% of tetrakis(dimethyl phosphate) 4. Impure material fromseveral similar preparations (1.6 g) was recrystallized by dissolving in20 mL of acetone, and adding about 30 mL of water. After standingovernight at 0° , 0.8 g of crystalline product 13 was collected. Thismaterial melted at 224-228° and was homogeneous by TLC and NMR. TLC(Solvent A): tris(phosphate) 13, Rf=0.73; tetrakis(phosphate) 4 0.66;starting material 2, 0.55.

¹ H-decoupled ³¹ P NMR δ=2.55, 2.11 and 1.96. ¹ H-NMR δ=7.6-8.2 (m, 10H,benzoate), 5.9 (m, 2H) 5.15 (q, 1H), 4.8 (m, 3H), 3.2-3.8 (m, 18 H,OCH₃), 2.2 (s, 3H, Ac). Step 2 Preparation of lithium myo-inositol1,4,5-tris(phosphate) (15)

A solution of recrystallized tris(dimethyl phosphate) 13 (1.20 g, 1.60mmol) in 10 mL of 30% hydrogen bromide in acetic acid was heated at 60°for 1 h. The reaction mixture was concentrated with a rotary evaporator(at about 1 mm and 40°). The residue was co-evaporated twice with water.The crude product was dissolved in water and the pH of the solution wasadjusted to 10.3 by the addition of 4M aqueous lithium hydroxide. Thebasic solution was added with vigorous stirring to ethanol. Theresulting mixture was allowed to stand for 1 h on ice, after which theprecipitate was collected by filtration, and washed with ethanol andether. A solution of the resulting intermediate dibenzoate 14 in 5 mL of1M lithium hydroxide was heated at 60° for 30 min. After cooling, thereaction mixture was added dropwise with stirring to ethanol. After 1 h,the resulting precipitate was collected by filtration and washed withethanol and ether to give 640 mg of the product 15, as a white powder.Gradient HPLC using phosphate detection indicated that this precipitatewas a 95:5 mixture of tris(phosphate) 15 (15.5 min) and inositolbis(phosphates) (8.13).

¹ H-NMR (pH 10) δ=4.37 (s, 1H, H2); 4.27 (app q, J =8.7, 1H, H4)3.95-4.1 (m, 3H, H1, 5,6): 3.83 (dd, J =2.5, 8.7, 1H, H3).

EXAMPLE 3. PREPARATION OF LITHIUM MYO-INOSITOL1,3,4,5-TETRAKIS{PHOSPHATE) (11)

Step 1. Preparation of 2,6-dibenzoyl-myo-inositol{2,4-dibenzoyl-myo-inositol} (7)

To a solution of 11.6 g of 3,6-dibenzoate 2 (30 mmol) in 120 mL ofpyridine at 100° was added 80 mL water. While monitoring by TLC, themixture was heated at 100° , until most of the 3,6 dibenzoate wasconverted to a mixture of 2,6 and 1,6 dibenzoates. After 2 h, thereaction was concentrated with a rotary evaporator and coevaporatedtwice with ethanol. The residue was triturated with ethanol and theethanol extract was concentrated to about 5 mL and filtered. Accordingto TLC (Solvent A), the ethanol extract was an approximately 20:10:1:1mixture of 2,6-dibenzoate 7; 1,6-dibenzoate; 3,6-dibenzoate 2; and anunknown material. The residual solid was 5.8 g (50%) of 3,6-dibenzoate2. Dichloromethane was added until the ethanol solution was turbid andthe mixture was stored at 0° overnight. Collection of the resultingprecipitate gave 1.10 g (10% yield) of 2,6-isomer 7.

TLC (solvent A) 2 Rf=0.55; unknown side product, 0.48; 7, 0.40; 1,6dibenzoate, 0.28. NOTE: A sample of 1,6-dibenzoyl inositol was obtainedby acid hydrolysis of 2,3:4,5-diisopropylidene-1,6-dibenzoyl inositol, aside product from the preparation of bisacetonide 1.

¹ H NMR of a similar preparation δ32 5.5 ppm (s, 1H, H2), 5.3 (t, 1H,H6), 3.9 (dd, 1H, H1) 3.7 (m, 2H, H3,4); 3.5 (t, 1H, H5). When thesignal at 5.3 ppm was irradiated, the signal at 3.9 (H1) collapsed to as and that at 3.5 to a doublet (H5)

Step 2. Preparation of 2,6-dibenzoyl-myo-inositol1,3,4,5-tetrakis(dimethyl phosphate) (9)

A 100-mL, round bottomed flask equipped with a magnetic stirrer bar andseptum cap was charged with 1.20 g of 2,6-dibenzoate 7 (3.1 mmol), 20 mLof methylene chloride and 5.2 mL (30 mmol) of dry diisopropylethylamine.After cooling the mixture to 0° on ice, 2.6 mL (24 mmol) of dimethylchlorophosphite was added during 2 min via syringe. The mixture wasremoved from the ice and the stirred for 30 min. The mixture wasrecooled to 0° , and 6 mL of 0.5M sodium phosphate at pH 7.0 and 10 mL(about 88 mmol, 28 eq) of 30% hydrogen peroxide were added. Theresulting two phase mixture was stirred vigorously for 10 min at 0° andthen 1 h at 25° . The layers were separated and the organic layer waswashed with phosphate buffer and water. After concentrating, the residuewas dissolved in ether and allowed to crystallize overnight. Thecrystals were filtered off and washed with ether to produce 1.50 9 oftetrakis(dimethyl phosphate) 9 as a white powder.

TLC (Solvent A) Rf=0.60. ¹ H-NMR (of material from a similarpreparation) δ=7.4-8.2 (m, 10H, benzoate); 6.2 (t, J=2.8, 1 H, H2); 5.9(t, J=10.2, 1H, H6); 5.02 (app. q, J=9.7, H4); 4.84 (dt,J=2.7,10.2 1H,H4); 4.75 (app q, J=9.4, 1H, H5); 4.58 (dt, J=2.7, 10.2, 1H, H3).

¹ H-decoupled ³¹ P-NMR δ=2.39, 2.35, 2.34, 1.64

Step 3. Preparation of lithium myo-inositol 1,3,4,5-tetrakis(phosphate)(11)

A solution of 1.05 g (1.6 mmol) of tetrakis(dimethyl phosphate) 9 in 10mL of 30% hydrogen bromide in acetic acid was heated at 60° for 30 min.The reaction mixture was concentrated with a rotary evaporator (at about1 mm and 40° ). The residue was co-evaporated twice with water. Theresidue was dissolved in water and the pH of the solution was adjustedto 10.0 with 1.0M aqueous potassium hydroxide. Gradient HPLC analysisshowed that this solution contained a single UV-absorbing peak at 29min, (10), and nothing that responded on the phosphate detection system.Addition of this solution to rapidly stirred ethanol gave a gum ratherthan a dry precipitate. The entire crude product was concentrated andheated with 3.8 mL of 1.0M aqueous potassium hydroxide at 80° for 1 h.After cooling, the solution was added dropwise with rapid stirring toethanol. After standing at 0° for 1 h, the resulting precipitate wascollected by filtration and washed with ethanol and ether to yield 850mg of crude potassium salt 11. Gradient HPLC using phosphate detectionshowed that this material was a 95:5 mixture of tetrakis(phosphate) 11,(retention time 24 min) and tris(phosphates) (15 min), with no responseon the UV detector at 240 nm. A portion (400 mg) of the crudeprecipitate was further purified by dissolving it in 20 mL water,adjusting the solution to pH 5 with Dowex 50 (H form), and adding thesolution to a 1×13 cm column of Dowex 1 X8 (100-200 mesh). Materialsadsorbed on the column were eluted with 90 mL of a linear 0.0-0.6Mlithium chloride gradient, at a rate of 1 mL/min. Tetrakis(phosphate) 11was eluted and resolved from the other products. The appropriatefractions (63-78 ml) were combined, adjusted to pH 11.0 with 1.0 Maqueous lithium hydroxide and evaporated to dryness. After thoroughwashing with ethanol (to remove lithium chloride), vacuum drying gave102 mg of tetrakis(phosphate) 11.

¹ H NMR of a similar preparation (DMSO+trifluoroacetic acid, 65°) δ=4.52(app. q, J=9.3, 1H, H4); 4.23 (s, 1H, H2), 4.23 (dt, J=2.5, 10.2, 1H,H3); 4.17 (app. q, J=8.9, 1H, H5); 4.02 (dt, J=2.5, 10.2, 1H, H1); 3.83(t, J=11, 1H, H6). With decoupling of phosphorous, the signals at 4.52,4.23 collapsed to triplets and the signal at 4.02 collapsed to a doubletof doublets, and changes are observed at 4.17. ³¹ P-NMR(DMSO+trifluoroacetic acid, 65° ) δ=1.015, 0.56, 0.42, 0.147.

EXAMPLE 4. PREPARATION OF MYO-INOSITOL 1,4,5,6-TETRAKIS (PHOSPHATE) (27)

Step 1. Preparation of 2,3-isopropylidene-myo-inositol1,4,5,6-tetrakis(dimethyl phosphate) (25)

A 100-mL, round bottomed flask equipped with a magnetic stirrer bar andseptum cap was charged with 1.30 g (5 mmol) of 2,3-isopropylidenemyo-inositol 24, 15 mL of dry methylene chloride and 6.0 mL (34.5 mmol,6.9 eq) of dry diisopropylethylamine. Dimethyl chlorophosphite (2.7 ml,25.1 mmol, 5.0 eq) was added dropwise at 20° . The mixture was stirredfor 30 min at 20°. After cooling to 0° , 12 mL of 0.5M pH 7.0 phosphatebuffer and 5 mL (about 43 mmol, 8.6 eq) of 30% hydrogen peroxide wereadded. After stirring vigorously for 30 min at room temperature, thephases were separated. The organic phase was washed twice with equalvolumes of a saturated aqueous sodium chloride, and then concentrated ona rotary evaporator to give 2.5 g of an oily residue. TLC analysis(90:10:1 dichloromethane-methanol-water) indicated that this materialcontained a major product, 25, (Rf=0.45) that was UV-inactive and acidcharrable, and a minor unknown UV-active impurity (Rf=0.50). Materialprepared in a similar fashion was apparently homogeneous by NMR.

¹ H NMR δ=1.4,1.6 (s, 3H, CH₃); 38 (m, 24H, OCH3); 4.42 (t, J=7.5, 1H);4.6-4.8 (m, 4H); 4.9 (m, 1H).

Step 2. Preparation of lithium myo-inositol 1,4,5,6-tetrakis(phosphate)(27)

A 15-mL test tube with standard tapered joint was charged with 0.5 g(about 1 mmol) of acetonide 25, 0.5 mL of dry dichloromethane and 1.2 mL(9.1 mmol, 9.1 eq) of bromotrimethylsilane (Aldrich). After stirring for30 min at 20° , solvent and by-products were removed by rotaryevaporation. The oily residue was stirred with 1.0 mL of water for 1 hat 20° to hydrolyze the ketal and then evaporated to dryness. Theresidue was dissolved in 1 mL of water, and the pH of the resultingsolution adjusted to 10.0 with 4.0M aqueous lithium hydroxide. Thissolution was added dropwise to 3 mL of ethanol. The resultingprecipitate was collected and washed with ethanol and ether, giving 216mg of tetrakis(phosphate) 27 as an amorphous powder. The product wasredissolved in 2 mL of water and reprecipitated as above to give 140 mgof dried product 27. This material was homogenous by HPLC.

HPLC: The product gave a single major peak (>95%) with the phosphatedetection system with a retention time of 24 min, characteristic of atetrakis(phosphate). H1-NMR of the free acid (i.e., prior to lithiumhydroxide treatment) from a similar preparation (d6-DMSO), 6 =3.58 (dd,J=2,10, 1H, H3); 3.88 (broad s, 1H, H2); 4.47 (app q, J=10, 1H);4.2-4.36 (m, 3H).

¹ H-NMR D₂ O+dl-TFA, pH<2, 60° ) δ=4.90 (app. q, J =9.3); 4.78 (app. q,J=10); 4.68-4.58 (m); 4.62 (s, H2); 4.1 (dd, J=2.7,9.7, H3). Withphosphorous decoupling, the signals at 4.9 and 4.78 collapsed tosinglets.

³¹ P NMR (D₂ O, pH 10, 55°) δ=6.65, 6.40, 6.03, 5.72.

What is claimed is:
 1. A myo-inositol phosphite of the formula ##STR5##wherein A¹ through A⁶ are independently selected from the groupconsisting ofH, a hydroxyl protecting group, and P(YR)(ZR¹), whereR andR¹ are, independently, a phosphate protecting group, Y and Z are,independently, selected from the group consisting of O, S, and NR²,where R² is aryl or a C₁ -C₁₅ straight chain, branched or cyclic alkylwhere the alkyl may be internally interrupted by ether oxygen, providedthat at least one of A¹ through A⁶ are P(YR)(ZR¹).
 2. A myo-inositolphosphite according to claim 1, wherein the phosphorus protectinggroups, R and R¹ are, independently, aryl, or a C₁ -C₁₅ straight chain,branched or cyclic alkyl, where the alkyl may be internally interruptedwith ether oxygen and where aryl or the alkyl may be substituted orunsubstituted with nitro, sulfonyl, halogen, ester and ketone groups. 3.A myo-inositol phosphite of the formula ##STR6## wherein A¹ through A⁶are independently selected from the group consisting ofH, a hydroxylprotecting group, and P(YR)(ZR¹),where R and R¹ are, independently, aphosphate protecting group, Y and Z are, independently, selected fromthe group consisting of O, S, and NR², where R² is aryl or a C₁ -C₁₅straight chain, branched or cyclic alkyl where the alkyl may beinternally interrupted by ether oxygen, wherein at least two of A¹through A⁶ are P(YR)(ZR¹).